693 research outputs found
ACTIVE SUPPRESSION OF IMMUNOGLOBULIN ALLOTYPE SYNTHESIS : II. TRANSFER OF SUPPRESSING FACTOR WITH SPLEEN CELLS
The mechanism of chronic allotype suppression in (SJL x BALB/c)F1 mice has been investigated by means of cell transfer studies. These mice are phenotypically negative for serum Ig-1b, the paternal allotype determinant on γG2a immunoglubulin, as a result of perinatal exposure to maternal anti-Ig-1b. When spleen or bone marrow (B) cells from suppressed mice were injected into irradiated BALB/c "indicator" hosts, detectable levels of Ig-1b were demonstrated in the sera of a majority of the recipients early after transfer. These results indicate that Ig-1b-producing cells or their precursors are present in the lymphoid tissues of suppressed mice, even though they are not expressed. Within 5–7 wk, it was no longer possible to detect Ig-1b in the sera of these hosts, although cells producing another paternal allotype (Ig-4b) were shown to persist. Control BALB/c mice, injected with spleen and B cells from normal mice, continued to produce high levels of immunoglobulin carrying this allotype. The disappearance of serum, Ig-1b occurred most frequently in the recipients of suppressed spleen cells. Similar results were obtained using a mixture of spleen cells from normal and suppressed mice. Ig-1b production in the recipient mice ceased within a few weeks, even though the majority of cells in the mixture were obtained from normal (nonsuppressed) donors. The data are interpreted as evidence that chronic allotype suppression in mice is actively maintained by cells which are resident in the lymphoid tissues, splenic cells being the most effective. These cells are capable of proliferating in a new host and exerting their suppressive influence on Ig-1b-producing cells and/or their precursors
TOLERANCE AND IMMUNITY TO MATERNALLY DERIVED INCOMPATIBLE IgG2a-GLOBULIN IN MICE
Progeny mice were confronted with maternal γ-globulin of a different allotype by either back-cross mating, intercross mating, or by foster nursing. In all cases, many mice subsequently produced alloantibodies directed against the incompatible maternal type of IgG2a-globulin. In one series of experiments, immunologic tolerance to the maternally derived γ-globulin was demonstrated to exist in the period before formation of spontaneous antibody. The state of tolerance was then lost, unless maintenance injections of foreign γ-globulin were given. These studies demonstrate in a natural situation that maternally derived foreign proteins can first induce a state of immunological tolerance which is followed, after disappearance of the antigen, by a state of immunity. As such, this parallels the experimental induction of tolerance to foreign proteins by neonatal injections
An improved cell-volume analyzer
Design and operation of cell-volume analyzer friction, glaze ice, and studded tire effects on highway
Human prostate specific and shared differentiation antigens defined by monoclonal antibodies.
Cell sorting in a Petri dish controlled by computer vision.
Fluorescence-activated cell sorting (FACS) applying flow
cytometry to separate cells on a molecular basis is a widespread
method. We demonstrate that both fluorescent and unlabeled live
cells in a Petri dish observed with a microscope can be
automatically recognized by computer vision and picked up by a
computer-controlled micropipette. This method can be routinely
applied as a FACS down to the single cell level with a very
high selectivity. Sorting resolution, i.e., the minimum distance
between two cells from which one could be selectively removed
was 50-70 micrometers. Survival rate with a low number of 3T3
mouse fibroblasts and NE-4C neuroectodermal mouse stem cells was
66 +/- 12% and 88 +/- 16%, respectively. Purity of sorted
cultures and rate of survival using NE-4C/NE-GFP-4C co-cultures
were 95 +/- 2% and 62 +/- 7%, respectively. Hydrodynamic
simulations confirmed the experimental sorting efficiency and a
cell damage risk similar to that of normal FACS
Fluorescence-activated cell analysis and sorting of viable mammalian cells based on beta-D-galactosidase activity after transduction of Escherichia coli lacZ.
Dissociation spectrum of H from a short, intense infrared laser pulse: vibration structure and focal volume effects
The dissociation spectrum of the hydrogen molecular ion by short intense
pulses of infrared light is calculated. The time-dependent Schr\"odinger
equation is discretized and integrated in position and momentum space. For
few-cycle pulses one can resolve vibrational structure that commonly arises in
the experimental preparation of the molecular ion from the neutral molecule. We
calculate the corresponding energy spectrum and analyze the dependence on the
pulse time-delay, pulse length, and intensity of the laser for nm. We conclude that the proton spectrum is a both a sensitive probe of the
vibrational dynamics and the laser pulse. Finally we compare our results with
recent measurements of the proton spectrum for 55 fs pulses using a Ti:Sapphire
laser (nm). Integrating over the laser focal volume, for the
intensity W cm, we find our results are in
excellent agreement with these experiments.Comment: 17 pages, 8 figures, preprin
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